Radiation curable coatings are currently being used in a wide variety of applications. It is desirable to use radiation curable coating systems because the need for conventional solvents is eliminated. This is, of course, highly beneficial because there are increasing demands to eliminate volatile organic compounds (VOC) from coating systems. Energy savings are also a strong driving force behind the use of radiation curable coating systems. Radiation curable coating systems also offer an advantage in that they can be applied to virtually any type of substrate. For instance, radiation curable coatings can be applied to plastic, glass, textile fabrics, leather, metal, paper, wood and a variety of other types of substrates.
Conventional radiation curable coating systems are comprised of an acrylic diluting monomer, an acrylic oligomer and a photocatalyst. Such conventional radiation curable coating systems typically have the rheological properties of a Newtonian fluid. Thus, they cannot typically be applied to substrates in non-horizontal or vertical applications or in thick layers. This is because such coatings have a tendency to run or sag before they can be cured. This has limited the used to radiation curable coatings to applications where they can be applied to the horizontal surface of substrates in relatively thin layers. It has accordingly precluded them from being used in coating three-dimensional objects. Furthermore, the rheological properties of conventional radiation curable coatings has limited the means by which they can be applied to substrates in industrial applications.
A means to modify the rheological properties of radiation curable coating compositions would be highly desirable. Such a technique could be used to make non-horizontal applications, spray applications or dip applications of radiation curable coatings possible. The ability to make thick coatings and to coat porous surfaces, such as paper, with minimal penetration into the substrate could also be achieved.